Injector mounting configuration for an exhaust treatment system

ABSTRACT

The present disclosure relates to a device for mounting an injector to an exhaust pipe. The device includes an injector mounting structure having an exterior surface configured for mounting the injector. The injector mounting structure also includes an interior surface arrangement defining an interior volume and a port for allowing the injector to inject a reductant into the interior volume. The interior surface arrangement is configured to prevent swirling of exhaust within the interior volume.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 12/617,301,filed Nov. 12, 2009, which application claims the benefit of provisionalapplication Ser. No. 61/114,119, filed Nov. 13, 2008, which applicationsare incorporated herein by reference in their entirety

TECHNICAL FIELD

The present disclosure relates generally to exhaust treatment systemsfor controlling exhaust emissions. More particularly, the presentdisclosure relates to systems for reducing NOx emissions from engineexhaust.

BACKGROUND

Selective catalytic reduction (SCR) systems are used to treat engineexhaust to provide a reduction in NOx emissions. Many SCR systems useammonia as a reductant for reducing NOx to N₂. A typical SCR systemincludes a substrate having a catalyst such as vanadium, titanium,platinum or other precious metal. In a typical NOx reduction reaction,the catalyst provided on the substrate promotes the reaction of ammoniawith NOx to form N₂ and H₂O. This reaction is favored by the presence ofexcess oxygen.

In certain SCR systems, a urea-water solution is provided as a reductantsource for use in the reduction of NOx. However, to function as aneffective reductant, the urea-water solution must be decomposed into auseable reductant form (i.e., ammonia). To decompose the urea-watersolution, the water in the solution is first removed throughvaporization. Next, the urea decomposes via thermolysis to formisocyanic acid (HNCO) and ammonia (NH₃). Finally, the HNCO decomposesvia hydrolysis to form NH₃ and carbon dioxide.

A problem with urea-based SCR systems is that urea and urea-by-product(e.g., cyanuric acid, biuret, melamine, ammelide, and ammeline) depositscan be formed within the exhaust system when decomposition of theinjected urea-water solution is incomplete. This deposition of urea andurea-by-products is particularly problematic when the urea-watersolution sprayed into the exhaust system is exposed to relatively lowtemperatures.

SUMMARY

One aspect of the present disclosure relates to an exhaust treatmentsystem for treating engine exhaust. The exhaust treatment systemincludes a reductant dispensing location at which a reductant isintroduced into the exhaust being treated. In one embodiment, thereductant dispending location is configured to reduce the likelihoodthat the reductant or by-products from the reductant are deposited insignificant amounts within the exhaust system.

A variety of additional aspects will be set forth in the descriptionthat follows. These aspects can relate to individual features and tocombinations of features. It is to be understood that both the forgoinggeneral description and the following detailed description are exemplaryand explanatory only and are not restrictive of the broad concepts uponwhich the embodiments disclosed herein are based.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a prior art configuration for mounting an injector to anexhaust pipe;

FIG. 2 shows an exhaust treatment system in accordance with theprinciples of the present disclosure;

FIG. 3 is a bottom plan view of the underside of an injector mountingstructure in accordance with the principles of the present disclosure;

FIG. 4 is an upstream end view of the injector mounting structure ofFIG. 3;

FIG. 5 is a cross-sectional view taken along section line 5-5 of FIG. 3;

FIG. 6 is a cross-sectional view taken along section line 6-6 of FIG. 3;

FIG. 7 is a plan view taken from viewing perspective 7-7 of FIG. 6;

FIG. 8 is a bottom plan view of an alternative injector mountingstructure in accordance with the principles of the present disclosure;

FIG. 9 is an upstream end view of the injector mounting structure ofFIG. 8;

FIG. 10 is a cross-sectional view taken along section line 10-10 of FIG.8;

FIG. 11 is a cross-sectional view taken along section line 11-11 of FIG.8; and

FIG. 12 is a plan view taken from section line 12-12 of FIG. 11.

DETAILED DESCRIPTION

The present disclosure relates generally to exhaust treatment systemsfor controlling engine emissions (e.g., diesel engine emissions). Incertain embodiments, exhaust treatment systems in accordance with theprinciples of the present disclosure include SCR systems used to controlNOx emissions generated from engines such as on-road or off-road dieselengines. Certain embodiments of the present disclosure include reductantdispensers (e.g., injectors) that dispense (e.g., spray) reductants intoan exhaust stream being treated by the exhaust treatment system. Inpreferred embodiments of the present disclosure, the exhaust treatmentsystem is configured to reduce the likelihood for the reductant orby-products of the reductant to form deposits at locations within theexhaust system. In one embodiment of the present disclosure, thereductant dispensed into the exhaust treatment system includes urea(e.g., a urea-water solution). However, it will be appreciated that thevarious aspects of the disclosure can also be applied to exhausttreatment systems dispensing other types of reductants or otherreactants.

FIG. 1 shows a prior art exhaust treatment system 20 including aninjector stand-off tube 22 mounted to an exhaust pipe 24 through whichexhaust in need of treatment is conveyed. The exhaust is conveyedthrough the exhaust pipe 24 in the direction indicated by arrows 26. Thestand-off tube 22 is mounted to the exhaust pipe 24 at a location inwhich the stand-off tube 22 covers an opening 28 defined through thewall of the exhaust pipe 24. The stand-off tube 22 includes an interiorsurface arrangement 23 that defines an interior volume 30. The interiorvolume 30 of the stand-off tube 22 is in fluid communication with theinterior of the pipe 24 through the opening 28. The stand-off tube 22includes an injector mounting location 32 at which an injector forinjecting reductant can be mounted. An injector mounted at the injectormounting location 32 is adapted to spray reductant (e.g., via a nozzle)into the interior volume 30 of the stand-off tube 22.

Referring still to FIG. 1, the interior surface arrangement 23 of thestand-off tube 22 includes an upstream interior surface 34 positioned atan upstream end 31 of the opening 28 and a downstream interior surface36 positioned at a downstream end 33 of the opening 28. The upstreaminterior surface 34 starts at the upstream end 31 of the opening 28 andangles away from the pipe 24 in a direction opposite to the direction 26of exhaust flow through the exhaust pipe 24. The downstream wall 36starts at the downstream end 33 of the opening 28 and angles away fromthe exhaust pipe 24 in a direction opposite to the exhaust flowdirection 26. This configuration of the upstream and downstream interiorsurfaces 34, 36 causes exhaust from the exhaust pipe 24 to swirl orcirculate within the interior volume 30.

Since the reductant from an injector mounted at the injector mountinglocation 32 is sprayed through the interior volume 30, portions of thereductant can become mixed/entrapped in the swirling exhaust and canremain in the interior volume 30 for extended periods of time therebyincreasing the likelihood that portions of the reductant will becomedeposited within the stand-off tube 22. Furthermore, the stand-off tube22 has an outer surface exposed to atmosphere which can cause cooling ofthe interior surface arrangement 23 of the stand-off tube 22 therebyexacerbating the deposition problem.

FIG. 2 shows an exhaust treatment system 120 in accordance with theprinciples of the present disclosure. The exhaust treatment system 120includes an exhaust conduit such as an exhaust pipe 124 through which anengine exhaust stream flows in a direction indicated by arrows 125. Theexhaust treatment system 120 also includes an exhaust treatment device126 such as an SCR substrate mounted within the exhaust pipe 124, and areductant dispenser such as an injector 128 for dispensing (e.g.,spraying) a reductant into exhaust stream at a reductant dispensinglocation upstream from the exhaust treatment device 126. The injector128 is mounted to the exhaust pipe via an injector mounting structure130 secured to an exterior of the exhaust pipe 124. The exhausttreatment system 120 further includes a spray redirector 132 and a flowmixer 124 that are mounted between the reductant dispensing location andthe exhaust treatment device 126. The injector 128 has a spray cone 129aimed generally toward the spray redirector 132 and the spray redirector132 is configured to reduce the likelihood for reductant to formdeposits within the exhaust pipe 124 at a location opposite from theinjector 128. The mixer 134 is configured to improve exhaust flowuniformity at an upstream face 136 of the exhaust treatment device 126.

The exhaust pipe 124 includes a pipe wall 140 defining a side opening142. The injector mounting structure 130 is secured to an exteriorsurface of the pipe wall 140 at a location in which the injectormounting structure 130 covers the side opening 142 of the pipe 124. Forexample, the injector mounting structure 130 includes a 143 base havinga base surface 144 that contacts the exterior surface of the pipe wall140 and that extends completely around a periphery of the side opening142. The base surface 144 can have a curvature C1 (see FIGS. 5 and 7)that matches a curvature defined by the exterior surface of the exhaustpipe 124 (e.g., the outer diameter of the exhaust pipe 124). In certainembodiments, the base 143 of the injector mounting structure 130 can bewelded or otherwise secured to the exterior surface of the exhaust pipe124.

The injector mounting structure 130 includes an interior surfacearrangement 148 defining an interior volume 150. When the injectormounting structure 130 is mounted to the exhaust pipe 124, the sideopening 142 of the exhaust pipe 124 provides fluid communication betweenthe interior of the exhaust pipe 124 and the interior volume 150 of theinjector mounting structure 130. The interior volume 150 is preferablyshaped to reduce or minimize the likelihood for exhaust to swirl orcirculate within the interior volume 150 for an extended period of time.Thus, rather than swirling, the flow can generally make a single passthrough the interior volume 150. This type of configuration assists inpreventing reductant (e.g., a water-urea solution) sprayed from theinjector 128 from depositing within the interior volume 150.

Referring to FIG. 2, the side opening 142 defined through the wall 140of the pipe 124 has an upstream end 161 and a downstream end 163. Asshown at FIG. 4, the interior surface arrangement 148 of the injectormounting structure 130 includes an upstream interior surface 164positioned adjacent the upstream end 161 of the opening 142, adownstream interior surface 166 positioned adjacent the downstream end163 of the opening 142, and an intermediate interior surface 168 thatprovides a transition between the upstream portion interior surface 164and the downstream interior surface 166. The upstream interior surface164 starts at the upstream end 161 of the side opening 142 and anglesoutwardly from the upstream end 161 of the side opening 142 in adownstream direction (i.e., in the same direction as arrows 125). Thedownstream interior surface 166 of the interior surface arrangement 148starts at the downstream end 163 of the side opening 142 and anglesoutwardly from the downstream end 163 of the side opening 142 in anupstream direction (i.e., the opposite direction of arrows 125). Theintermediate interior surface 168 provides an angle transition betweenthe upstream interior surface 164 and the downstream interior surface166. The relative arrangement of the surfaces 164, 166 and 168 helps toreduce recirculation of exhaust within the interior volume as comparedto prior art systems such as the prior art system shown at FIG. 1.

In the depicted embodiment, the injector mounting structure 130 includesan upstream wall 170 that defines the upstream interior surface 164 andalso defines an exterior injector mounting surface 172. The upstreamwall 170 is depicted as being generally straight such that the upstreaminterior surface 164 and the exterior mounting surface 172 each have agenerally planar configuration. The planar configuration of the exteriorinjector mounting surface 172 facilitates securing the injector 128thereto. Referring to FIGS. 4 and 7, the exterior injector mountingsurface 172 has a generally triangular configuration. An injector nozzlereceiving opening 174 or port is defined through the upstream wall 170for receiving a nozzle 176 of the injector 128. The opening 174preferably has a depth selected such that a tip of the nozzle 176 isgenerally flush with the upstream interior surface 164 when the injector128 is mounted to the exterior injector mounting surface 172. Theinjector mounting structure 122 also includes features for facilitatingfastening or otherwise securing the injector 128 to the exteriorinjector mounting surface 172. For example, as shown at FIG. 7, theupstream wall 170 defines a plurality of attachment holes 180 that arespaced around the injector nozzle receiving opening 174. The attachmentholes 180 can include blind holes that are internally tapped withthreads so as to be configured to receive fasteners such as bolts usedto secure the injector 128 to the injector mounting structure 122.

The downstream interior surface 166 has a curvature C2 (shown at FIG. 6)that extends in a direction parallel to a central axis 121 of theexhaust pipe 124, and a curvature C3 (shown at FIG. 5) that extends in adirection transverse to the central axis 121 of the exhaust pipe 124.The curvature C2 preferably has a larger radius than the curvature C3.The curvature C2 extends along a length L1 of the interior volume 150 ofthe injector mounting structure 122 while the curvature C3 extendsacross a width W1 of the interior volume 150. The length L1 ispreferably greater than the width W1. In one embodiment, the length L1is at least 1.5 times or at least 2 times as great as the width W1. Thelength L1 is defined as the maximum length of the interior volume 150and the width W1 is the maximum width of the interior volume 150. Thecurvature C1 of the base preferably has a larger radius than thecurvature C3 and a smaller radius than the curvature C2.

The intermediate interior surface 168 provides an angular transitionbetween the upstream interior surface 164 and the downstream interiorsurface 166. The intermediate interior surface 168 is depicted in FIG. 6can have a curvature in a direction parallel to the central axis 121, orcould be planar.

Referring to FIG. 4, the upstream interior surface 164 preferablydefines an angle α relative to the central longitudinal axis 121 of theexhaust pipe 124. In one embodiment, the angle α is in the range of 20to 60 degrees. In another embodiment, the angle α is in the range of 30to 50 degrees. In still another embodiment, the angle α is about 40degrees.

Referring still to FIG. 4, the downstream interior surface 166 definesan angle β relative to the central longitudinal axis 121 of the exhaustpipe 124. In one embodiment, the angle β is in the range of 10 to 50degrees. In another embodiment, the angle β is in the range of 40 to 20degrees. In still another embodiment, the angle β is about 28 degrees.In certain embodiments, the angle α to be larger than the angle β toassist in mounting the injector to the injector mounting structure at adesired angle relative to the exhaust pipe while maintaining suitableflow-through characteristics. In one embodiment, the angle α is at least1.5 times larger than the angle β.

The intermediate interior surface 168 defines a transition between theupstream interior surface 164 of the downstream interior surface 166. Asshown at FIG. 4, the intermediate interior surface 168 defines an angleθ relative to the upstream interior surface 164. In one embodiment, theangle θ is in the range of 130 to 170 degrees. In another embodiment,the angle θ is in the range of 140 to 160 degrees. In still anotherembodiment, the angle θ is about 153 degrees.

Referring to FIG. 3, the interior volume 150 of the injector mountingstructure 130 has a boundary 190 defined by an inner edge 191 of thebase surface 144 that is generally teardrop shaped. The width W1 (i.e.,the maximum width) of the interior volume 150 is located at theintermediate interior surface 168. From the maximum width W1, the widthof the interior volume 150 tapers inwardly as the interior volume 150extends in either an upstream or downstream direction. From the widthW1, the width of the interior volume 150 has a steeper taper angle asthe interior volume extends in an upstream direction and a more gradualtaper angle as the interior volume extends in a downstream direction.

Referring again to FIG. 4, the interior volume 150 also has a depth D1that is smaller than the length L1. The depth D1 is defined as a maximumdepth of the interior volume 150. In certain embodiments, the length L1is at least 1.5 times as large as the depth D1. In other embodiments,the length L1 is at least 2 times as large as the depth D1. In oneembodiment, the length L1 is in the range of 3 to 6 inches, the depth D1is in the range of 0.5 to 1.5 inches, and the width W1 is in the rangeof 1 to 3 inches.

It is preferred for the nozzle of the injector 128 to be aimed such thatthe spray of reductant impinges upon the spray redirector 132 ratherthan the side of the exhaust pipe 124 that is located opposite from theinjector 128. The spray redirector 132 is preferably made of a materialthat facilitates a high rate of heat transfer from the exhaust to thespray redirector. In this way, the spray director, which is locatedinside the exhaust pipe 124 and does not have significant surface areaexposed to outside air, remains hot. Therefore, the spray from theinjector 128 is directed at hot surfaces that do not encourage thedeposition of the reductant. This is in contrast to the wall of theexhaust pipe 124 that has an outer surface exposed to cool air which cancause cooling of the wall 124. It is noted that in FIG. 2, a portion ofthe stream from the injector 128 is aimed partially at the oppositeportion of the bottom wall of the exhaust pipe 124. However, it will beappreciated that the flow of exhaust within the exhaust pipe 124 willcarry this portion of the spray into the spray redirector 132 such thatcontact with the bottom wall of the exhaust pipe 124 is avoided. Thespray redirector 132 can have a variety of different configurations suchas a wire mesh disk, a porous disk, a perforated plate, a mixer plateincluding a plurality of vanes, fins, or louvers, a fibrous disk, asubstrate having axial passages/channels defined by corrugated metalsheets, or other structure.

In certain embodiments, it is desirable to reduce or minimize theinterior volume defined within the injector mounting structure. In oneexample embodiment, the interior volume of the injector mountingstructure is less than 3.5 cubic inches.

FIGS. 8-12 show an alternative injector mounting structure 130′ inaccordance with the principles of the present disclosure. The injectormounting structure 130′ includes an interior volume 150′ having a lengthL2, a width W2, and a depth D2. The interior volume 150′ is generallydome-shaped and has a curvature C4 of constant radius that extends alongthe entire length L2 of the interior volume from an upstream end 161′ tothe downstream end 163′. The interior volume 150′ also has a curvatureC6 in the direction of the width W2. The curvature C5 is providedthroughout the entire interior surface of the injector mountingstructure 130′. Additionally, an upstream surface 164′ of the interiormounting structure 130′ has an exhaust entrance angle x that isgenerally equal (i.e., equal or about equal) to an exhaust exit angle ydefined by a downstream surface 166′ of the injector mounting structure130′. In certain embodiments, the angles x and y are each in the rangeof 10-50 degrees. The injector mounting structure 130′ also includes abase 142′, an exterior injector mounting location 172′, and a port 174′for receiving an injector nozzle.

What is claimed is:
 1. A device for mounting an injector to an exhaustpipe, the device comprising: an injector mounting structure having anexterior surface configured for mounting the injector, the injectormounting structure also including an interior surface arrangementdefining an interior volume, the injector mounting structure furtherincluding a port for allowing the injector to inject a reductant intothe interior volume, the interior surface arrangement being configuredto prevent swirling of exhaust within the interior volume.
 2. The deviceof claim 1, wherein the interior volume includes a length that extendsfrom an upstream end to a downstream end of the interior volume, whereinthe interior surface arrangement includes an upstream interior surfacethat starts at the upstream end of the interior volume and anglesoutwardly from the upstream end of the interior volume in a downstreamdirection.
 3. The device of claim 2, wherein the interior surfacearrangement includes a downstream interior surface that starts at thedownstream end of the interior volume and angles outwardly from thedownstream end of the interior volume in an upstream direction.
 4. Thedevice of claim 2, wherein the upstream interior surface is planar. 5.The device of claim 3, wherein the interior volume includes a width thatis transverse relative to the length, wherein the downstream interiorsurface has a first curvature that extends along the length of theinterior volume and a second curvature that extends along the width ofthe interior volume.
 6. The device of claim 5, wherein the firstcurvature has a larger radius of curvature than the second curvature. 7.The device of claim 5, wherein the downstream interior surface definesan angle relative to a longitudinal axis of the exhaust pipe in therange of 10-50 degrees.
 8. The device of claim 3, wherein the downstreaminterior surface defines an angle relative to a longitudinal axis of theexhaust pipe in the range of 20-40 degrees.
 9. The device of claim 3,wherein the upstream interior surface defines an angle relative to alongitudinal axis of the exhaust pipe in the range of 20-60 degrees. 10.The device of claim 2, wherein the upstream interior surface defines anangle relative to a longitudinal axis of the exhaust pipe in the rangeof 30-50 degrees.
 11. The device of claim 3, wherein the upstreaminterior surface defines a first angle relative to a longitudinal axisof the exhaust pipe, wherein the downstream interior surface defines asecond angle relative to the longitudinal axis of the exhaust pipe, andwherein the first angle is larger than the second angle.
 12. The deviceof claim 11, wherein the first angle is at least 1.5 times as large asthe second angle.
 13. The device of claim 1, wherein the interior volumeis dome-shaped.
 14. The device of claim 13, wherein the interior surfacearrangement defines a curve of generally constant radius that extendsalong a length of the interior volume from a downstream end to anupstream end of the interior volume.
 15. The device of claim 3, whereinthe upstream interior surface and the downstream interior surfacerespectively define an exhaust entrance angle and an exhaust exit anglethat are generally equal.
 16. An exhaust treatment system comprising: anexhaust conduit; an injector mounting structure mounted to an exteriorsurface of the exhaust conduit, the injector mounting structure havingan exterior injector mounting surface, the injector mounting structurealso including an interior surface arrangement defining an interiorvolume in fluid communication with an interior of the exhaust conduit,the injector mounting structure further including a port extendingthrough the injector mounting structure from the exterior injectormounting structure to the interior volume, the interior surfacearrangement being configured to prevent swirling of exhaust within theinterior volume; an injector mounted at the exterior injector mountingsurface, the injector including a nozzle positioned adjacent the port ofthe injector mounting structure; and a spray redirector positionedwithin the exhaust conduit, the nozzle of the injector being oriented sothat spray from the nozzle impinges upon the spray redirector.
 17. Thedevice of claim 16, wherein the nozzle includes a tip that is generallyflush with a surface of the interior surface arrangement.